This invention relates generally to techniques in building and launching ships and more particularly to a system whereby ships are built and launched with efficient utilization of the dock and ship building areas associated therewith.
The methods of building and launching ships can be roughly divided into two categories, one utilizing an inclined ship-building slip or berth from which a completed ship is launched into the sea or open water, and the other utilizing a ship-building dock from which a completed ship is launched by opening the dock gate and filling the dock with water.
In either of these cases, the floor areas on which ships are built should have sufficient strength to bear the weight of the ships, and for the purpose of efficiently utilizing these ship building floor areas, various methods have been proposed.
According to one of these methods often referred to as a block ship-building method, various sections of a ship constructed separately at different ship building areas are transported to a ship-building berth or to a ship-building dock to be finally assembled into a ship therein, thereby to shorten the ship building period in the berth or dock and to effectively utilize the berth or dock of high building cost only for the assembly of a ship at the final stage.
According to another method, in view of the fact that the stern part of a ship which includes an engine room requires a longer construction period than the other parts of the ship, the stern part is constructed separately in an area adjacent to the ship building berth and then shifted to the berth, and, subsequently, the remaining part of the ship is constructed in the berth. Otherwise, while a first ship is being constructed in a ship building dock, the stern part of a second ship is also constructed separately in the same ship building dock, and after the first ship has been completed and launched, the stern part of the second ship is utilized to complete the second ship which is to be launched after the launching of the first ship.
A further method of building and launching ships is disclosed in Japanese patent publication No. 25893/1971 (Pat. No. 642,908) entitled "ship Hull Construction Method and System." According to this method, a dry dock whose two ends are openable toward open water through respective gates is provided, and while a first ship is being constructed in the dry dock, the stern part of a second ship, which is to be launched after the launching of the first ship, is also constructed in the same dry dock in tandem relationship to the first ship, whereby the period for building the second ship with its hull occupying substantially the entire area of the dry dock is shortened, and the utilization of the dry dock is made more efficient.
A characteristic feature of this method is that the construction of the stern part of the second ship is started at one of the two longitudinally opposite end positions in the dry dock selected alternately while the construction of the first ship is carried out in the remaining part of the dock, and when the first ship is completed it is launched through the dock gate at the other end position of the dock while when the second ship is completed it is launched through the dock gate at the one end position of the dock. When the first ship is to be launched, an intermediate removable gate is installed to divide the dock into two sections, containing the first ship and the stern part of the second ship, respectively, and water is introduced into the one section of the dock in which the first ship is positioned, so that the first ship can be launched through the gate associated with the one section of the dock.
In all of the above described known methods and systems, a dry dock of high cost of construction and use is used and occupied for a long period for the construction of a ship, and it cannot be used for other ships as long as the ship is being constructed. In this sense, the known methods and systems are not economical.